Update workflow for changes in benchmark tooling

Google's Benchmark project has rearranged some of the files we need for
the testing workflows. This commit points pip towards to correct
requirements.txt for the latest versions of the framework.

Author: mosullivan93

.github/workflows/c-cpp.yml

@@ -84,7 +84,7 @@ jobs:
       run: |
         git clone https://github.com/google/benchmark.git
         cd benchmark
-        pip3 install -r requirements.txt
+        pip3 install -r tools/requirements.txt
         cmake -E make_directory "build"
         cmake -E chdir "build" cmake -DBENCHMARK_ENABLE_GTEST_TESTS=OFF -DBENCHMARK_ENABLE_TESTING=OFF -DCMAKE_BUILD_TYPE=Release ../
         sudo cmake --build "build" --config Release --target install